HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) References Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by HERRIN, E. Articles by RICHMOND, J. Search for Related Content GeoRef GeoRef Citation

On the propagation of the Lg phase

Abstract

Empirical determinations of the mean surface velocity of Lg indicate a range from 3.47 to 3.54 km/sec., with one set of velocities off the east coast of Mexico as low as 3.20 km/sec. Computations based on ray theory show that Lg with these velocities may be shear waves guided in the upper crust by an alternation of refractions and surface reflections. The slower velocities would result from shear waves traveling almost entirely in the sedimentary layer. Polarization of Lg is related to the angle at which the guided shear waves are incident at the surface.

Calculations show that Lg would travel in a continental crust covered by a considerable thickness of water, thus supporting the hypothesis that the absence of Lg indicates that an oceanic crust underlies such bodies of water as the Gulf of Mexico.

All computations were run on the Univac 1103 at Southern Methodist University.

Footnotes

The authors are, respectively, of the Department of Geology and Geophysics, and of the Computing Laboratory, at Southern Methodist University.

This article has been cited by other articles:

				E. Zor, E. Sandvol, J. Xie, N. Turkelli, B. Mitchell, A. H. Gasanov, and G. Yetirmishli Crustal Attenuation within the Turkish Plateau and Surrounding Regions Bulletin of the Seismological Society of America, February 1, 2007; 97(1B): 151 - 161. [Abstract] [Full Text] [PDF]

				D. E. McNamara, T. J. Owens, and W. R. Walter Propagation characteristics of Lg across the Tibetan Plateau Bulletin of the Seismological Society of America, April 1, 1996; 86(2): 457 - 469. [Abstract] [PDF]

				P. W. POMEROY, W. J. BEST, and T. V. MCEVILLY Test ban treaty verification with regional data--A review Bulletin of the Seismological Society of America, December 1, 1982; 72(6B): S89 - S129. [Abstract] [PDF]

				L. M. DORMAN Seismic crustal anisotropy in Northern Georgia Bulletin of the Seismological Society of America, February 1, 1972; 62(1): 39 - 45. [Abstract] [PDF]

				R. G. BAKER Determining magnitude from Lg Bulletin of the Seismological Society of America, December 1, 1970; 60(6): 1907 - 1919. [Abstract] [PDF]